FLOEAS OF SECOND AEY AND TERTIARY PERIODS. 47 1 



Meek, Hayclen, Cope, and Stevenson, are of opinion that the 

 fauna carries more weight than the flora, and that the Fort 

 Union or Lignitic series should be regarded as truly the 

 summit of the Cretaceous. To this view Prof. Newberry, 

 who is in the rare position of having attained almost equal 

 eminence in Pala30zoology and Paleobotany, gives his ad- 

 hesion ; and it is to be considered as in every respect the 

 most probable view, if we take into account the fact that 

 the disputed series is admittedly overlain unconformably by 

 strata of undoubted Tertiary age. Upon the whole, then, 

 when we take into consideration the general unreliability of 

 terrestrial or fresh-water Mollusca as tests of age, and also 

 the often unsatisfactory nature of stratigraphical conclusions 

 based upon vegetable remains only, we can hardly avoid 

 arriving at the opinion that the Great Lignitic series of 

 North America is truly Cretaceous, though probably of a 

 later date than any of the recognised Cretaceous deposits of 

 the Old World. 



Admitting that the " Lignitic Formation " of Western 

 North America is truly of Cretaceous age, it follows that 

 the Lower and Upper Cretaceous rocks are, from a botanical 

 point of view, sharply separated from one another. The 

 Palaeozoic period, as we have seen, is characterised by the 

 prevalence of " Flowerless " plants {Cryptogams), its higher 

 vegetation consisting almost exclusively of Conifers. Tlie 

 Mesozoic period, as a whole, is characterised by the preva- 

 lence of the Cryptogamic group of the Ferns, and the Gymno- 

 spermic groups of the Conifers and the Cycads. Up to the 

 close of the Lower Cretaceous, no Angiospermous Exogens 

 are certainly known to have existed, and Monocotyledonous 

 plants or Endogens are very poorly represented. With the 

 Upper Cretaceous, however, a new era of plant-life, of which 

 our present is but the culmination, commenced, with a great 

 and apparently sudden development of new forms. In place 

 of the Ferns, Cycads, and Conifers of the earlier Mesozoic 

 deposits, we have now an astonishingly large number of true 

 Angiospermous Exogens, many of them belonging to existing 

 types ; and along with these are various Monocotyledonous 



